1. Field of the Invention
This invention relates generally to the collection and presentation of optical information and, more particularly, to the acquisition, processing, and hard copy presentation of optical information obtained from a plurality of viewing or sensing angles.
2. Statement of the Problem
The collection and study of optical information is integral to a variety of activities. These activities include, without limitation, airborne and satellite surveillance and monitoring of areas of interest. The collected information is typically digitized on the platform on which the cameras or other optical sensors are mounted, pre-processed and sent by downlink for further processing. The information is often formatted and printed for visual inspection as well. For example, aerial photographs may be studied by skilled persons, both to identify items missed by computer recognition methods and to obtain further information not conveniently or accurately obtained by computer methods.
The 2-dimensional picture has shortcomings. One is that it is 2-dimensional, which has aesthetic and related functional drawbacks. More particularly, the viewer does not obtain a sense of depth from a 2-dimensional picture, and this failure may cause a misinterpretation of information that a 3-dimensional view would have provided.
Another shortcoming with existing art airborne and satellite surveillance systems, and the hard copy images they produce, is that the images show the photographed ground area only as seen from one position and viewing angle that it was originally obtained. For example, a photograph of a ten-foot diameter hole obtained by overflying it with a camera looking down at an angle of 45 degrees with respect to a flight path may fail to present an image of the contents of the hole.
One possible solution to the above example problem is to fly over the item of interest, i.e., the hole, twice, with the camera looking straight down on the second flyover. Other possible solutions include mounting a plurality of cameras on the airborne or satellite platform, or mounting a camera on a steerable gimbal, and thereby obtain a plurality of pictures of a particular ground area, each from a different viewing angle.
There are problems with the above-identified potential solutions. One is that even if a plurality of pictures is obtained, each of the pictures is two-dimensional. The previously identified problems with two-dimensional images remain. Another problem is that assigning a plurality of pictures to cover the various viewing angles of each ground area of interest requires the user to keep track of, and have the burden of viewing, a plurality of hard copy pictures. This creates further problems. One is the overhead caused by the user having to keep track of multiple pictures. Another is that the pictures may not be aligned or registered with respect to one another. For example, the viewer may have a hard copy of a first picture of a ground area, taken from a first airborne surveillance viewing angle, in which a building of interest is situated in, for example, the upper left corner of the copy. A second picture of the same ground area, taken from a second viewing angle, may show the building in its upper right corner. Still another problem, which relates to the previously identified problem, is that the viewer must change his or her visual focus continually, namely by looking at the pictures taken from one viewing angle and then looking at the pictures taken from another viewing angle. This can be inconvenient. It also increases the probability of human error, as the user must remember how something looked from one viewing angle as he or she shifts attention to another hard copy showing how the item appeared from another viewing angle.
The existing art does provide a type of stereoscopic visual surveillance method, in which two frames of information are captured via satellite and transmitted to, for example, the National Reconnaissance Office (NRO). Printable images of the left and right frames are then generated, one being polarized orthogonal to the other, arranged above one another and printed. The user wears polarizing glasses, whereby his or her left eye sees the left image and his or her right eye sees the right image. The user thus sees an apparent three-dimensional image.
However, there are numerous problems with this method. One is that each polarized image pair shows, and is limited to, the ground area of interest as seen from an oblique viewing angle. More particularly, a typical stereoscopic image is formed by mounting two cameras on a satellite. One camera is ahead of the satellite, at a depression angle toward the earth. The other camera looks behind the satellite, at the same depression angle. Therefore, the left image and the right image are each obtained by looking at the ground area of interest at an oblique viewing angle. For this reason the prior art stereoscopic image does not have a direct look-down angle. This can have significant results. Prior art FIG. 1 shows a simulated example of an image of a building 2 as if viewed in its original polarized format through polarized glasses. For purposes of comparison, FIG. 4 is a microlens hard copy of the same building, displaying two three-dimensional views generated and fixed in hard copy in accordance with a method of the present invention. FIG. 1 does not reveal any object proximal to the building 2. One of the two viewing angles provided by FIG. 4, though, reveals a missile 4. The missile 4 cannot be seen in FIG. 1 because it is close against a side wall of the building 2, and the FIG. 1 stereoscopic image was obtained from oblique viewing angles.
Another shortcoming with the prior art stereoscopic views is that, even with the polarizing glasses, only one three-dimensional view of the ground area of interest can be seen from a single hard copy. Therefore, the previously discussed problems of a single viewing angle image are increased. They are increased because not only is the user required to look at multiple hard copies to see what an area or building looks like from different viewing angles, but the pictures are difficult to identify without wearing the glasses. The glasses cause further problems, namely eye fatigue and equipment overhead.